Moving function call into explicit Task allows sending?

Using Swift
1

Output from swift --version with strict checking enabled etc.:

swift-driver version: 1.115 Apple Swift version 6.0 (swiftlang-6.0.0.9.10 clang-1600.0.26.2)

Is someone able to explain why lines marked A1 and C1 are not allowed? I don't understand why moving them into an explicit Task changes anything. Am I missing something?

import SwiftUI
import Observation

struct SendRequestView: View {
    @Bindable var config: Config
    var body: some View {
        Text("Hello")
            .task { await sendRequest(config: config) }
    }

    // This is MainActor
    private func sendRequest(config: Config) async {
        // let apiResponse = try? await NetworkAPI.sendRequest(config: config) // A1. Not allowed.
        let apiResponseIsolated = try? await NetworkAPI.sendRequestIsolated(config: config) // B1. Allowed.
        // let apiResponseNonIsolated = try? await NetworkAPI.sendRequestNonIsolated(config: config) // C1. Not allowed.

        // A1 and C1 error
        // Sending 'config' risks causing data races
        // Sending main actor-isolated 'config' to nonisolated static method 'sendRequestNonIsolated(config:)' risks causing data races between nonisolated and main actor-isolated uses
        // Sending main actor-isolated 'config' to nonisolated static method 'sendRequest(config:)' risks causing data races between nonisolated and main actor-isolated uses

        Task {
            // This is MainActor
            let apiResponse = try? await NetworkAPI.sendRequest(config: config) // A2. Allowed.
            let apiResponseIsolated = try? await NetworkAPI.sendRequestIsolated(config: config) // B2. Allowed.
            let apiResponseNonIsolated = try? await NetworkAPI.sendRequestNonIsolated(config: config) // C2. Allowed.
        }
        // ...
    }
}
enum NetworkAPI {
    static func sendRequest(config: Config) async throws -> APIResponse {
        let urlRequest = URLRequest(url: config.url)
        let urlSession = URLSession(configuration: .ephemeral)

        let response = try await urlSession.data(for: urlRequest)

        return APIResponse(response: response)
    }

    static func sendRequestIsolated(config: Config, isolation: isolated (any Actor)? = #isolation) async throws -> APIResponse {
        let urlRequest = URLRequest(url: config.url)
        let urlSession = URLSession(configuration: .ephemeral)

        let response = try await urlSession.data(for: urlRequest)

        return APIResponse(response: response)
    }

    nonisolated static func sendRequestNonIsolated(config: Config) async throws -> APIResponse {
        let urlRequest = URLRequest(url: config.url)
        let urlSession = URLSession(configuration: .ephemeral)

        let response = try await urlSession.data(for: urlRequest)

        return APIResponse(response: response)
    }
}
@Observable
final class Config: Identifiable, Codable {
    var id: UUID = UUID()
    var url: URL
    init(url: URL) { self.url = url }
}
struct APIResponse {
    let data: Data
    let urlResponse: URLResponse
    init(response: (Data, URLResponse)) {
        data = response.0
        urlResponse = response.1
    }
}
2

Seems like the issue I've reported to me, here it's even more subtle as the @MainActor declaration is hidden behind the View protocol.